The present invention relates to die cutting machines for making carton blanks, and more particularly to a bracket for properly locating a lower blanking tool with respect to a pull-out frame during a blanking operation in a carton die cutting machine.
In the manufacture of cartons, small sheets of paper material having specific profiles are cut out of larger sheets of paper material. These smaller sheets are known as carton blanks which, in turn, are formed into cartons and/or boxes. The blanks are formed during a process known as a blanking operation in a die cutting machine.
In a die cutting machine, the blanks are cut, but not removed from a large sheet of paper material. After the blanks have been cut, the sheet is moved downstream in the die cutting machine to a blanking station where the sheet is positioned over a lower tool or frame assembly for support. The lower tool or frame assembly includes an outer frame and an inner grid having large openings which correspond in size, in shape and in position to the profile of the carton blank previously cut. The lower tool is mounted on a pull-out frame, and below the pull-out frame is a mechanism for stacking the carton blanks.
At the blanking station, an upper tool is used in combination with the lower tool or frame assembly to knock the carton blanks from the sheet of paper material while holding the scrap material that surrounds the blanks. The upper tool has a support board that moves vertically up and down in the die cutting machine, and the support board typically has a plurality of stand-offs depending therefrom that hold pushers spaced beneath the board which in turn are used to push the carton blanks from the sheet through the lower tool or frame assembly. A plurality of presser assemblies are also mounted in the support board and depend therefrom to hold the scrap material against the lower tool or frame assembly during the blanking operation so that the blanks may be pushed from the sheet. A presser assembly typically includes a presser rail which is biased downwardly away from the support board by a spring so that the rail is positioned slightly below the pushers. As the upper tool is lowered, the presser rail engages the sheet of paper material first such that a scrap portion of the large sheet of material is secured between the presser rail and the frame. The upper tool then continues to be lowered such that the sheet of material engages the inner grid within the frame while at substantially the same time the pushers engage the carton blanks and knock the blanks out of the sheet of material and through the inner grid. The carton blanks then fall into a stacking mechanism below the frame where the blanks are stacked for further processing.
The frame and grid of the lower tool support a sheet of paper material during the blanking operation, and thus the grid must be configured to match or conform to the desired die cut in the sheet of paper material. Also, the lower tool must be properly positioned with respect to the pull-out frame so that the grid is properly positioned with respect to both the upper tool and the stacking mechanism. In addition, the grid and outer frame must be disassembled, reconfigured and reassembled whenever a different carton blank needs to be produced. Unfortunately, due to manufacturing tolerances, ineffective clamping devices and the like, outer frames are not always “square” with respect to the pull-out frame. In addition, the grid may not always be positioned with high precision within the outer frame since the clamping pieces which hold the lower tool onto the pull-out frame can move slightly during assembly and thus alter the desired position of the grid.